1. Field of the Invention
The present invention relates to a shearing method using a punch press and to a die used therein, and more particularly to a half-cutting shearing method, wherein the shearing cut is made without the full length of a blade.
2. Description of the Prior Art
Conventionally, a numerically-controlled, turret type punch press is used in obtaining a plurality of items such as a chassis for electronic equipment cut from standard-sized plate. With this type of equipment, many types of punch and die pairs are provided on upper and lower turrets, and these are successively exchanged to process the desired holes in the plate at the desired positions. Finally, the process of cutting out the contoured sections is performed using the nibbling method.
This method has considerable merit in that the semi-processed goods are automatically obtained by processing the desired holes within the area of the plate in a single clamping operation but, on the other hand, the following negative points exist. Specifically, because of the fact of cutting out contours by means of overlapping punched holes, such as round holes and square holes, in the nibbling process, the yield from the plate is low. Further, in the case of round holes, the result is unsatisfactory because of the wave form at the edge of the cut.